Lock the Screen with a Screensaver after 15 Minutes of Inactivity
A screensaver must be enabled and set to require a password to unlock. The timeout should be set to fifteen minutes of inactivity. This mitigates the risk that a user might forget to manually lock the screen before stepping away from the computer.
A session time-out lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system, but does not log out because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, operating systems need to be able to identify when a user's session has idled and take action to initiate the session lock.

Parameter: Number of seconds

Technical Mechanism: To check if the system has a configuration profile configured to enable the screen saver after a time-out period, run the following command:
system_profiler SPConfigurationProfileDataType | grep idleTime
The check should return a value of '900' or less for idleTime. If not, this is a finding.